This invention relates to an improved fastener of the hook and loop type and a method for producing the same using a combined extrusion/roll forming process. The assignee of this application is owner of U.S. Pat. No. 4,775,310 which describes an apparatus for making a separable fastener and U.S. Pat. No. 4,872,243 which describes the product produced by the apparatus of the former patent. Striplike fasteners of the type described in the subject patents comprise a great multiplicity of closely spaced upstanding hooklike projections to releasably engage loops of a companion fastener strip to form a cyclable or semipermanent closure sold in the trade under the brand name Velcro(copyright). Depending upon the configuration of the multihook fastener, many different types of material are adapted for coaction therewith to effect joining of the structures to which the strip fasteners are themselves joined. Such fastener devices are finding broad usage in such diverse applications as securing automotive seat covers to foamed seat buns, closures for food bags, the application of armor to military vehicles and holding down floor coverings to floors.
Each of the recited applications and many more, well known to those skilled in the art, require the fastener to be permanently attached to a second article such as a piece of textile fabric, a seat bun, a floor or the flap of a paper bag. Sewing, however, is limited as to the nature of the material to which the fastener may be attached. Adhesive systems have long been used as a principal method of attaching fasteners to other objects as well. U.S. Pat. No. 3,773,580 discloses a method of securing a fastener member to a substrate by first applying a synthetic resin adhesive to one side of the base of a fastener, opposite the side containing the upstanding engaging elements, and then applying an adhesive to the substrate. Thereafter the adhesive coating on the fastener is activated. The two adhesive coated surfaces are brought together in face to face relationship to firmly affix the fastener member to the substrate. The subject patent teaches that xe2x80x9cin order to securely bond an adhesive to the tape member it is preferred that the opposite surface of the tape member have a suitable base coat which would provide for a secure bond between the tape member and the adhesivexe2x80x9d. U.S. Pat. No. 3,726,752 instructs that in preparing adhesive laminates, wherein synthetic resin based adhesive is laminated to a web of polyamide polymer, it was found that strong bonding between the polyamine substrate and the adhesive lamina were difficult to achieve, and the prior art is xe2x80x9cwell-studded with attempts to overcome this problemxe2x80x9d. This patent overcomes such difficulties by treating the polyamide web with primer coating consisting of a complex chemical mixture in a solvent medium to render an improved bonding surface. Many patents, including U.S. Pat. Nos. 2,349,290 and 3,060,070 and 3,111,448 and 2,766,164, describe methods for bonding poly(amide) polymer to specific surfaces primarily natural or synthetic rubber. All of these teachings rely upon chemical means for enhancing the ability to bond to the surface of a sheet or fibrous material.
Many plastic fastener tapes are produced from plastic materials possessing the minimum strength and resiliency essential to the proper functioning of the hooklike projections. Customarily the side of the fastener tape opposite the upstanding hooks is a smooth, flat, uniform and regular surface difficult to bond, as is well documented in the prior art. Such difficulties present particular problems for hook and loop fasteners. This class of products are convenience products and if it is necessary to amply complex chemical treatments to the tape prior to bonding the convenience advantage is lost. It is known to apply pressure sensitive adhesives to such fasteners by the application of corona treatments in the manufacturing facilities where the fastener tapes are manufactured but such treatments are not available for many users and do not present a reasonable solution for creating a fastener surface which is readily bondable to a wide variety of surfaces using a wide range of adhesive types. U.S. Pat. No. 3,594,865 describes an apparatus for continuously forming a flexible web with molded protuberances of plastic maternal incorporated in a base web. The base of the web is either a porous woven or nonwoven fabric, or an extruded film. The supporting fabric is impregnated with molten plastic simultaneously as hooks are formed. While U.S. Pat. No. 3,594,865 is sparse in detail concerning the nature of the product formed from the apparatus it does characterize the impregnation of the base fabric as complete, stating in appropriate part, xe2x80x9ca liquid moldable plastic material, for example a molten plastic, is injected into the hook molding recesses of the wire and also onto the surface and into the interstices of the base fabric which lies on the surface of the drum.xe2x80x9d The base fabric passes under a nozzle which impregnates it with the same plastic used to inject the dies used to form the plastic hooks with the clear implication the porous base web is completely saturated with the plastic. This is considerably different from the products of the present invention wherein the process controls the distribution of plastic into the backing material to a degree necessary to firmly hold the backing material to the base of the hook sheet but does not encase the backing to destroy it""s aesthetic characteristics as a functioning backing material to modify the back surface of the fastener. The backing of U.S. Pat. No. 3,594,865 is primarily a support onto which hooks are formed and does not modify the backing of the fastener to receive adhesives or gluing agents nor is it possible to utilize loop materials as the backing material to form back to back fasteners. It is also known to use complex laminating methods to add a bondable surface to many sheet materials but such methods are expensive and often create a final product which has undesirable characteristics such as bulk, stiffness, a tendency to delaminate, operating temperature limitations or other properties making the laminate undesirable.
A product using such techniques, well known in the art of hook and loop fasteners, is the so called back to back fastener. Such a product is created by taking a hook fastener and a loop fastener and bonding the two together in a back to back relationship such that the resulting laminate has hooks on one side and loops on the other side. Such a combination finds wide use in many strapping operations such as wire ties, plant ties and fastener straps for holding splints and the like in place. The limitation of such products in the past has focused on the method used to laminate the two components together as described above. The bulk created by the adhesive bonding of such laminates has clearly limited its usefulness.
Therefore it is the object of the present invention to produce a hook portion of a hook and loop fastener system which has a surface opposite the surface containing the upstanding hooks substantially modified in its characteristics from the customary flat, smooth, even surface which has little compatibility for bonding to other materials. A further objective of the invention is to create a surface on the back of a base of a plastic hook and loop fastener which will readily accept bonding agents such as adhesives, glues, cements and the like without special treatment of the surface. It is a further objective of the invention to create a loop surface on the back portion of the base of a plastic hook fastener which is capable of engaging into hooks on the front surface thereof to form a back to back laminate with less bulk, stiffness and thickness.
The process described in U.S. Pat. No. 4,794,028 for making plastic hooks utilizes an apparatus described in U.S. Pat. No. 4,775,310 comprising xe2x80x9ca first cooled unitary forming roller having a plurality of hook forming cavities defined in the periphery thereof and extending inwardly therefrom; a second pressure roller positioned for coaction with said first forming roller; means for concurrently rotating said first and second rollers in opposite directions about their generally respective axis; means for forming s striplike extrusion of molten plastic material adjacent said first and second rollers to be directed therebetween at an interface thereof such that said plastic material fills said hook forming cavities and forms a striplike member having a base portion and a great multiplicity of hooklike projections extending from one surface of said base portion and integral therewith; means for removing said striplike member from said first forming roller at a position spaced from the interface of said first and second rollers such that said hooklike projections are withdrawn from said hook forming cavities without opening said cavities after being cooled by the first forming roller to a desired temperature.xe2x80x9d I have found it possible to introduce into the nip, formed by the two cylinders, various sheet materials which will become an integral part of the striplike material on the side opposite the hooks. Surprisingly, introduction of such materials into the nip along with the molten plastic does not interfere with the operation of the process and while certain cautions and limitations are, of course, desirable, the formation of such insitu laminates proceeds to great advantage. I have found a very wide variety of materials, such as nonwoven fabrics, woven and knitted textiles, reinforcing yarns, scrims and nettings, sheets of paper, plastic films, metallic window screening and almost any material in filmlike or thin sheet form can be handled in this manner. The formation of the striplike plastic fastener sheet insitu with a porous foreign backing most often is accomplished by infusion of the molten plastic into the structure of the web material where there is an intimate intermingling of the plastic within the pores of the web. In the case of nonporous films, the films tend to melt on their surface forming an intermolecular diffusion which forms a strong bond between the sheets. The inclusion of such foreign materials provides a substantial advantage over prior art methods of creating laminates. Such striplike materials contain no foreign material; the bonds are strong and a wide range of materials may be joined in this way. Additionally, the process of adding the backing at the time of creating the hooks offers economic advantages over the more conventional processes of creating a laminate using adhesives or other bonding agents in second stage processes.